Field of the Invention
The present invention relates to an air intake structure for a saddle-ride type vehicle. For example, the present invention is preferable to be employed for a saddle-ride type vehicle such as a motorcycle.
Description of the Related Art
A motorcycle employs what is called a ram-air system that directly guides travelling air to an air cleaner box to improve air intake efficiency.
Patent Document 1 discloses an air intake structure where the travelling air introduced through a front end air intake port of an air inlet duct flows into a head portion with ram pressure, and is divided in right and left at the head pipe part to flow into right and left main frames, and simultaneously, a part of the travelling air flows into both air intake ducts.
Patent Document 2 discloses an air intake structure where the travelling air introduced through an air intake port of a front cowl flows through a front duct of an air duct, an inner duct in a main frame, and an intake passage in a rear duct to be taken into an engine as combustion air from an air box portion.
Patent Document 1: Japanese Patent No. 4340500
Patent Document 2: Japanese Patent No. 4964618
The air intake structures disclosed in Patent Document 1 and Patent Document 2 use the ram pressure generated during high-speed running to raise an intake air pressure in the air cleaner box for improving the air intake efficiency. However, there is a problem that it is difficult to increase an intake air flow rate into the air cleaner box during low-speed or middle-speed running that generates no ram pressure. In the case where a cross-sectional area of a duct is expanded to increase the intake air flow rate during low-speed or middle-speed running, the vehicle width is widen to result in a disadvantage in a design and aerodynamic.